The use of rotary potentiometers for controlling electronic devices is well known in the art. One common application is the volume control used in car stereos, two-way radios, and the like. The electronic device uses the output of the potentiometer to determine the output level desired by the user. In some implementations, a variable control function, such as volume control, is combined with the on-off switch for the device in a single potentiometer mechanism. A single knob, mechanically connected to the potentiometer, is used as the interface to the user. Typically, the entire knob is pushed to switch the device on or off, while the knob is rotated to vary the volume, or any other variable which is being controlled by the knob. This arrangement, though fairly common, presents some reliability and manufacturability problems which have not been adequately addressed in the art.
In a volume control application, the knob is usually attached to the volume pot which provides mechanical support. After repeated use, mechanical or electrical failure of the volume pot may occur because of an over stressed mechanical connection. When the volume control also includes the device on-off switch, the application of an axial force on the switch by the user can sever solder joints or other electrical connections, thereby shortening the life of the switch assembly. Additionally, the volume pot oftentimes has a rotational limit which defines the maximum and minimum selectable volume level. Excess rotational force applied to the volume pot can cause damage to the volume pot with the possibility of rendering the switch useless.
With some knob assemblies, inadvertent actuation of a device control may be likely. When the knob controls power to the device, inadvertent actuation may result in the draining of the power source. Other knob assemblies can be unintentionally disassembled by pulling on the knob with an insubstantial force. These issues ultimately affect a user's perception of the quality of the device.
A more effective knob assembly, which incorporates solutions to the above-mentioned problems should not increase manufacturing cost or complexity. A cost efficient manufacturing process requires simple operations while utilizing a minimum number of parts, thereby facilitating the assembly operation. Thus, an improved knob assembly for a potentiometer is required which protects the potentiometer from unnecessary stress, which provides enhanced user-friendliness, and which can be manufactured more efficiently.